1. Field of the Invention
This invention relates to a locking device for doors and the like, and more particularly to such a device for cooperation with a conventional dead bolt lock set whereby a door or the like may be locked in fully closed position or in partially opened position or may be unlocked for full opening.
2. Description of the Prior Art
Locking devices for permitting partial or full opening of a door are well known in the art. However, such devices known to me are relatively complicated structurally or functionally, the most common type employing a chain permanently connected at one end to a door or jamb and releasably connected at the other end to the other such member. While such devices are structurally simple, they are often difficult for the aged or handicapped to operate because the releasable end of the chain must be rather precisely manipulated in respect of a small keyhole-shaped opening to secure or release the chain. Other arrangements, such as those disclosed in U.S. Pat. Nos. 1,015,222, 1,037,377, 2,407,900 and 2,704,684, are comprised of a relatively large number of parts which contribute to high cost and complexity of operations especially for persons with physical infirmities.